ICTS Foundation Day Lectures: The future of our universe by Ashoke Sen

Foundation day lectures

The future of our universe

Speaker: ashoke sen (icts – tifr, bengaluru)

Date: 27 december 2021, 17:30 to 19:00

Venue: chandrasekhar auditorium, icts

Discovery of dark energy in the late 90's has changed our understanding of how the universe evolves. In this talk, I shall describe what it implies for our universe billions of years from now.

Table of Contents (powered by https://videoken.com)
0:00:00 The Future of Our Universe
0:07:15 Conclusion
0:07:42 We have known for about 100 years that our universe is expanding
0:09:00 The universe was thought to contain three kinds of sources of energy (mass) density:
0:10:03 In 1998 two independent experiments made a profound discovery.
0:10:34 Best explanation available today:
0:11:51 Dark energy' has now become a household word.
0:12:30 The classical story
0:12:44 Presence of dark energy causes the universe to undergo an accelerated expansion
0:14:06 Due to the accelerated expansion it is physically impossible for us to reach very faraway places in the universe.
0:15:28 The idea of multiverse is a reality even if it sounds like a science fiction.
0:17:17 In special theory of relativity we learn that
0:21:40 Conformal space-time diagram:
0:29:30 Even though the expansion of the universe pulls comoving objects apart,
0:30:57 In the far future,
0:32:18 The Quantum Story
0:32:22 The story begins with that of a particle sliding on a hill.
0:33:43 Our interest will not be in a particle, but in the whole universe.
0:34:20 A familiar example: Magnetic field (Bx, By, Bz)
0:35:03 Unlike magnetic field it has only one component which we shall
0:38:01 The properties of these two phases are typically very different.
0:39:38 Let us recall the case of a particle on a hill.
0:40:07 Can a similar tunnelling happen in a quantum field theory?
0:44:14 The surface begins an accelerated expansion, converting the potential difference to kinetic energy.
0:45:20 What will be the fate of any living or non-living object in A during this process?
0:46:21 This possibility has been known for about 50 years.
0:47:02 When we write the theory of the Higgs field, we write a nice form
0:48:52 But the situation is much more complicated.
0:49:39 1. Supersymmetry has been very useful in addressing many issues in particle physics.
0:52:36 Are we living in a false vacuum?
0:53:04 'String theory' is an attempt to have such a fundamental theory
0:54:00 If string theory is right then one of these minima describes the phase of the theory we are living in.
0:54:42 How do we know if we are living in a false vacuum?
0:55:44 Assuming that we are living in a false vacuum,
0:58:58 2. Calculate the volume of space-time between the past light-cone at and at t + it
1:01:21 Probability of being hit: h(t) it
1:03:09 Since theory cannot tell us the actual risk, can we invoke experiment?
1:04:18 Suppose one day a small asteroid hits the earth and destroys everything within 100 meter radius of impact.
1:05:03 I hope you would agree that the possibility, however small, that
1:05:46 As in most adventures, we need to leave home.
1:05:55 Let us recall some of the facts we learned.
1:07:03 If the rate of universe production exceeds the rate of destruction,
1:07:35 If we remain confined within our galaxy then our annihilation probability will be controlled by the rate of destruction.
1:08:24 We can overcome this fate if we spread out into the currently accessible universe.
1:10:04 Note that dark energy is the hero of the story.
1:10:52 Conclusion
1:11:11 Dark energy helps those who help themselves.
1:11:30 Q&A

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